This invention relates to the safety system of an industrial robot.
In general, in an industrial robot which automatically performs a welding job or a painting job on a product, a traversing job on an article being assembled, or the like, a safety system is provided to prevent the hand device of the robot from causing damage due to an impact, even when the hand device has collided against an object in the surroundings on account of the malfunction of a PCU (central processing unit) or other component when the robot is in a teaching mode or full-automatic operation.
Such a safety system of an industrial robot is known in the prior art, for example, the system described in Japanese Utility Model Registration Application Publication No. 55-53357. A hand device is connected with the free end of the arm of the industrial robot through an L-shaped fixture, the bent portion of which is formed with a groove. When the hand device collides with an object in the surroundings and receives an external force, the L-shaped fixture is cut by a stress concentrated in the groove, and the hand device comes off so as to avoid causing damage. Another safety device is disclosed in U.S. Pat. No. 4,673,329 commonly assigned with the present application.
With the prior-art safety system as described above, the excessive external force to which the hand device is subjected by an impact is avoided by the cutting of the L-shaped fixture. It is difficult to similarly avoid external forces in the horizontal direction and in the vertical direction. Thus, the prior-art system does not function satisfactorily as a safety system of an industrial robot which operates in three dimensions.